The Max-232 IC is started by the maxim integrated products in 1987. It is an integrated circuit which converts the signals from the RS232 serial port to the proper signal which are used in the TTL compatible digital logic circuits. The MAX232 can convert the signals like RX, TX, CTS, and RTS and it is a dual driver/receiver. The driver increases the output voltage levels of TIA232 from a 5 volt supply to 7.5 volts by using the external capacitor and on chip charge pumps. The receiver reduces the input levels of the TIA232 from 25 volts to the standard voltage level, i.e. 5volts of TTL levels and there is a threshold of 1.3 volts and hysteresis of 0.5 volts for the receiver. Further the max232 IC is extended by the four receivers and transmitters simultaneously with eight receivers and transmitters which are MAX238 and MAX248 and there are many combinations of receivers and transmitters.
What is a MAX232 IC?
The MAX-232 IC is an integrated circuit which consists of 16 pins and it is a resourceful IC mostly used in the voltage level signal problems. Generally, the MAX-232 IC is used in the RS232 communication system for the conversion of voltage levels on TTL devices that are interfaced with the PC serial port and the Microcontroller. This IC is used as a hardware layer converter like to communicate two systems simultaneously. The image of MAX232 is shown below.
What is an Interfacing?
An interfacing is a microprocessor which is used to connect various peripherals to carry out various operations to get a preferred output. There are two different types of interfacing first one is memory interfacing and the other one is I/O interfacing.
The memory interface is used for the microprocessor to access the memory which is continuously stored in the memory in the form of reading and writing data. It is used for specific register for reading and writing the data in the memory chip. I/O interfacing is done by the inputs which are keyboards and display monitors are outputs with the microprocessor.
Pin Description of MAX-232 IC
The MAX-232 IC is used to exchange the TTL/CMOS logic to RS232 logic levels through the serial communication of Microcontroller with the personal computers. The microcontroller operates at the TTL logic levels with the voltage of 0-5v, and the serial communication with PC works on the RS232 with the volts of -25V to +25V. The difference of voltage will become the makes difficult to establish the communication with each other.
The in-between links are provided through the MAX232 interface, it is a transmitter/receiver which includes the voltage generator to the supply of RS232 voltage levels through the 5V supply. The RS232 input converts to 5V TTL/COMS level through these receivers, i.e. R1 and R2 do not exclude the +-30V. The transmitters T1 and T2 are used to convert the TTL/COMS input levels to RS232 level.
The transmitter obtains input from the microcontrollers and microprocessors through serial transmission pins and the output is given to the receiver of RS232. The receiver on the other side obtains the input from transmission pin of RS232 serial port and the output is given to the receiver pin of the microcontroller. The external capacitor is added to the MAX232 with a range of 1µF to 22µF.
The pin configuration of MAX232 and the description of the each pin of is discussed in the tabular form.
|1||C1 +||Positive Voltage Multiplier Unit of External Capacitor|
|2||C3 +||Positive Voltage Multiplier Unit of External Capacitor|
|3||C1-||Negative Voltage Multiplier unit of External capacitor|
|4||C2 +||Positive Voltage Multiplier Unit of External Capacitor|
|5||C2 –||Negative Voltage Multiplier unit of External capacitor|
|6||C4-||Negative Voltage Multiplier unit of External capacitor|
|7||T2 Out||Transmitter data Output from RS232|
|8||R2 In||Receiver Data Input from RS232|
|9||R2 Out||Receiver Data Output from TTL logic level|
|10||T2 In||Transmitter Data Input from TTL logic level|
|11||T1 In||Transmitter Data Input from TTL logic level|
|12||R1 Out||Output of Receiver Data from TTL logic level|
|13||R1 In||Input of Receiver Data from RS232|
|14||T1 Out||Transmitter Output from RS232|
|16||Vcc||Power supply voltage|
Construction of MAX-232 IC
The MAX232 consist of 16 pins with 3 major blocks. The power supply of this integrated circuit is 5V which is compatible with most of the embedded systems. In the three major blocks, the first block is a voltage doubler by using the IC switched capacitor techniques are used to make the voltage doubler. If once the voltage is doubled, then the second block is converted to +10V and -10V. The main function of voltage level is converted in the 3rd block which consists of the two transistors and 2 receivers. The following diagram shows the construction of the MAX232.
Different Types of MAX-232 IC
There are two different types of MAX232 IC’s are MAX232N and the other one is MAX232D. Where in the MAX232N “N” represents the PDIP package style and it is used widely with low price. In the MAX232D “D” represents the SOIC package this type of packages is used correctly by the trained professionals.
MAX-232 IC Interfacinng
There are different types of MAX232 interface which are shown below with clear information and diagrams
PC Serial Port Communication by using MAX-232 IC
The following diagram gives the information about the PC serial port communication through the MAX232 interface. We can see the DB9 packages to the desktops and some old laptops. From the DB9 package pins we can use only two pins which are transmitter (Tx) and receiver (Rx)
The diagram consists of two drivers once the driver is used for circuit purpose and the other one is second drive it is used for the other purpose. There are two pins, i.e. Pin 11 and pin 12 are obtained from the TTL data and these two pins are attached to the Microcontroller.
GSM Modem Communication
There are different types of GSM modems are available in the market and the common GSM mode, which is common or mostly using in the market is TTL logic and sometimes some are using the RS232 standards by using this there is a problem in communication with GSM modem which is used by the Microcontroller, Aurdino, and some TTL platform. BY using the MAX 232 we can overcome the problems.
GSM/GPRS is used for the communication between a computer and a GSM/GPRS system. The GSM system is an architecture, it is used in most of the countries for the communication purpose. The next extension of GPRS is GSM it shows the higher transmission rate. The GSM/GPRS is composed by the power supply circuit and communication interface by using MAX232 interface and USB etc.
The GSM/GPRS is a device of wireless modem that is used for the communication purpose by using the SIM (Subscriber Identity Module) card, we can activate the communication of the network and also by using the IMEI (International Equipment Identity) serial number we can identify. The operations of the GSM/GPRS are mentioned below.
- Receiver, send messages to a SIM
- Read, search phone book entries in the SIM
- Make or Reject the Voice calls
By using the AT commands the modem is interfacing with the processor and the Microcontroller which communicate with the serial communication. The commands are from the Microcontroller and microprocessor. After receiving the commands to the modem, gives the output. There are different types of AT commands used by the modem and they are sent through the processor, controller, computer to interface with the GSM/GPRS cellular network.
Connections of 8051 to RS232
In this part we will discuss about the connection of the 8051 to RS232 connectors. In this the RS232 standard is not transistor transistor logic compatible, hence it requires the drivers such as the MAX232 chip to convert the voltage levels of RS232 and also in the opposite operation. The main intention of this topic to discuss about the interfacing of 8051 with the RS232 voltage levels to TTL level connectors through the MAX232.
RxD and TxD Pins of 8051
The 8051 Microcontroller has two pins which are used for the transmitting and receiving the data continuously. The two pins are TxD and RxD these two pins are pin11 and pin10 to the 8051 Microcontroller and these are from the port 3. The two pins are TTL compatible, hence it requires line drivers to make it as an RS232 compatible.
The RS232 is not a compatible in the microprocessors and microcontrollers using through the voltage converter we can convert the RS232 signal to TTL voltage which are acceptable to the 8051 pins i.e. TxD and RxD. The MAX232 converts the voltage levels of RS232 to TTL voltage and the operation is done in vise versa. We can see once example of a converter is MAX232 from Maxim Corp. The power supply of MAX232 and 8051 Microcontroller has same power supply, i.e. +5v hence we don’t use the dual power supplies
The below diagram shows the line drivers from the transmitting and receiving data and the line drivers TxD is called as a T1 and T2.
Applications of MAX-232 IC
- Interface Transactions
- Low power modes
- Battery powered RS232 system
- RS232 networks
- Portable Computing
This article discusses about what is the MAX232 and interfacing needs. I hope the given information in the article is helpful to give some good information and understanding the project. For more details if you have any queries regarding this article or to implement electrical and electronic projects you can comment in the below section. Here is a question for you, what is the function of MAX232?